Detection method and system based on polarization information

Abstract

The application relates to the field of optical technology and discloses a detection method and system based on polarization information, which are used for accurately positioning an orientation angle parameter of an optical component associated with polarization information. The method comprises the following steps: placing a detected object between a laser light source and a rotatable polarization beam splitter; the polarization beam splitter is used for simultaneously converting a polarized light beam emitted by the detected object into P light and S light, the light intensity distribution ratio of which dynamically changes during the rotation process; after the polarization beam splitter, an image acquisition device is used to acquire and calculate the light intensity distribution ratio of the P light and the S light which dynamically changes during the rotation process; when the light intensity distribution ratio is 1, a first orientation angle corresponding to the polarization beam splitter is determined; then, according to the relative relationship between the polarization direction angle of the light beam corresponding to the detected object when the light intensity distribution ratio is 1 and the orientation angle of the polarization beam splitter, the corresponding orientation angle parameter of the detected object is positioned.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a detection method and system based on polarization information. Background Technology

[0002] In sophisticated optical structures, precisely positioning the orientation angles of components is a common challenge. For example, virtual reality technology, after several years of development, has reached the third generation of the "pancake" approach. By attaching polarizers and quarter-wave plates to a transparent substrate, light is converted into left- or right-hand circularly polarized light, allowing light to pass through the thinnest structure to achieve a large refractive power, suitable for the eye's optical path. Therefore, ensuring the precise alignment of the polarizer and wave plate's orientation angles during application and installation is a crucial testing step.

[0003] Most existing methods for detecting the polarization direction of polarizers involve rotating the polarizer with a high-precision rotary motor and recording the light intensity values ​​at different polarization angles. Figure 1 The extreme points on the intensity-angle curve are used to distinguish the orientation angle. However, this method has low accuracy and efficiency. Another method is to directly mount the polarization measuring instrument on a high-precision rotary motor and deduce the orientation angle by measuring the various components of the Stokes parameter. Since polarization measuring instruments are mature, this method can be set up quickly; however, the detection accuracy of commercially available polarization measuring instruments has an error of 0.5°, resulting in high investment but unsatisfactory accuracy. Summary of the Invention

[0004] The purpose of this invention is to disclose a detection method and system based on polarization information, so as to accurately locate the orientation angle parameters of optical components associated with polarization information.

[0005] To achieve the above objectives, the method disclosed in this invention includes:

[0006] The object to be tested is placed between a laser source and a rotatable polarization beam splitter; the polarization beam splitter is used to simultaneously convert the polarized beam emitted from the object to be tested into P-beams and S-beams, whose intensity distribution ratio changes dynamically with the rotation process.

[0007] After the polarization beam splitter, an image acquisition device is used to acquire and calculate the intensity distribution ratio of P-light and S-light dynamically changing during the rotation process;

[0008] When the light intensity distribution ratio is 1, determine the first orientation angle corresponding to the polarization beam splitter; then, based on the relative relationship between the polarization direction angle of the emitted beam corresponding to the object being tested when the light intensity distribution ratio is 1 and the orientation angle of the polarization beam splitter, locate the corresponding orientation angle parameter of the object being tested.

[0009] Preferably, the object being detected is a first linear polarizer, and the orientation angle parameter located by detection is the polarization direction.

[0010] Preferably, the object to be detected is a phase delayer placed between the second linear polarizer and the polarization beam splitter, and the orientation angle parameter of the phase delayer is located in the fast axis direction; wherein, the second linear polarizer is a standard component with a known polarization direction and is deployed between the laser source and the polarization beam splitter, and the second linear polarizer is stationary during the rotation of the polarization beam splitter.

[0011] To achieve the above objectives, the present invention also discloses a detection system based on polarization information, which is based on the same technical concept as the above method, and includes:

[0012] An object to be detected is placed between a laser source and a rotatable polarization beam splitter; the polarization beam splitter is used to simultaneously convert the polarized beam emitted from the object to be detected into P-beams and S-beams with a dynamic change in intensity distribution ratio during rotation.

[0013] An image acquisition device deployed after the polarization beam splitter is used to acquire and calculate the intensity distribution ratio of P-light and S-light dynamically changing during the rotation process;

[0014] The control host, which is connected to the image acquisition device and the motor that drives the polarization beam splitter to rotate, is used to determine the first orientation angle corresponding to the polarization beam splitter when the light intensity distribution ratio is 1; then, based on the relative relationship between the polarization direction angle of the emitted beam corresponding to the object being detected when the light intensity distribution ratio is 1 and the orientation angle of the polarization beam splitter, the corresponding orientation angle parameter of the object being detected is located.

[0015] Preferably, the polarization beam splitter and the image acquisition device are fixed on the same rotary displacement stage.

[0016] The present invention has the following beneficial effects:

[0017] 1. When the light intensity distribution ratio is 1, P-light and S-light are most sensitive to changes in polarization angle, which can maximize the detection accuracy.

[0018] 2. By using a single image acquisition device to simultaneously acquire the light intensity information of P-light and S-light, the errors caused by synchronous acquisition by multiple detectors and time-division acquisition by a single detector are avoided, thereby further improving the accuracy of the detection orientation angle parameter.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a schematic diagram of the light intensity-angle curve in existing methods for detecting the polarization direction of polarizer orientation.

[0022] Figure 2 This is a schematic diagram of the detection method based on polarization information disclosed in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram showing the change of light intensity with angle when the orientation angle of the Wollaston prism and the polarizer are at different angles, as disclosed in the embodiments of the present invention. Detailed Implementation

[0024] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0025] Example 1

[0026] This embodiment discloses a detection method based on polarization information, such as... Figure 2 As shown, it includes the following steps:

[0027] Step S1: The object to be tested is placed between the laser source and the rotatable polarization beam splitter; the polarization beam splitter is used to simultaneously convert the polarized beam emitted from the object to be tested into P-beam and S-beam with the intensity distribution ratio dynamically changing with the rotation process.

[0028] In this step, a monochromatic laser source is preferred; the polarization beam splitter can be a Wollaston prism, which will be referred to as a prism for convenience.

[0029] Step S2: After the polarization beam splitter, an image acquisition device is used to acquire and calculate the intensity distribution ratio of P-light and S-light as they dynamically change during the rotation process.

[0030] Step S3: Determine the first orientation angle corresponding to the polarization beam splitter when the light intensity distribution ratio is 1; then, based on the relative relationship between the polarization direction angle of the emitted beam corresponding to the object being tested when the light intensity distribution ratio is 1 and the orientation angle of the polarization beam splitter, locate the corresponding orientation angle parameter of the object being tested.

[0031] In this step, it is assumed that the object being detected is a linear polarizer, and the orientation angle parameter used for detection and positioning is the polarization direction. According to Malus's law, for linearly polarized light with intensity I(0), after passing through the linear polarizer, the intensity of the transmitted light (ignoring absorption) is I = I(0)cos2θ; where θ is the angle between the vibration direction of the incident linearly polarized light and the polarization analysis direction of the polarizer. Therefore, as... Figure 3 As shown, when the orientation angle of the Wollaston prism (or simply prism) is parallel or perpendicular to the orientation angle of the polarizer, I s and I p The light intensity values ​​measured are 0° (or 180°) and 90° respectively. Theoretically, the light intensity distribution ratio R is either infinite or 0.

[0032] When the prism orientation angle is 45° or 135° (or can be considered as -45°) to the polarizer orientation angle, I s and I p The light intensity values ​​measured were at 45° and 135° (or -45°), respectively, and theoretically R = 1.

[0033] from Figure 3 As can be seen, when the prism orientation angle is 45° or 135° to the polarizer orientation angle, the light intensity is most sensitive to changes in angle, and more accurate detection data can be obtained than from other orientation angles. Moreover, in this system, I... s and I p Since the data is acquired simultaneously, disturbances to light intensity and detectors are largely avoided compared to other time-sharing acquisition schemes and schemes that acquire data synchronously with two detectors.

[0034] As a variation, the object to be detected may optionally be a phase delayer (such as a half-wave plate and a quarter-wave plate) placed between the second linear polarizer and the polarization beam splitter, wherein the orientation angle parameter of the phase delayer is located in the fast axis direction by detection; wherein the second linear polarizer is a standard component with a known polarization direction and is deployed between the laser source and the polarization beam splitter, and the second linear polarizer is stationary during the rotation of the polarization beam splitter.

[0035] The essence of the above-described transformation lies in treating the second linear polarizer and the phase retarder as a whole as a polarization direction selector similar to the first linear polarizer. Then, based on the similarity principle of the first linear polarizer's orientation angle, the orientation angle parameters corresponding to the phase retarder are deduced from the known polarization direction of the second linear polarizer and parameters such as the thickness of the phase retarder. This deduction is a technique conceivable based on the properties and principles of optical components. For example, if the object being tested is a half-wave plate, the bisector between the first orientation angle positioned by the polarization beam splitter and the second polarizer's orientation angle is the fast axis direction detected and positioned by the half-wave plate; this will not be elaborated further.

[0036] For a quarter-wave plate, when the polarization angle of the incident light is perfectly parallel to its fast axis angle, the transmitted light remains linearly polarized. When there is a slight deviation between the two angles, the transmitted light becomes "elongated" elliptically polarized light, and the major axis of the ellipse is the fast axis of the wave plate. As the angle approaches 45°, the elliptically polarized light gradually becomes circularly polarized light, and the change in light intensity with the angle becomes less and less significant. Therefore, preferably, in this embodiment, during the installation of the second linear polarizer and the phase retarder, the angle between the polarization direction of the second linear polarizer and the fast axis direction of the phase retarder is estimated to be less than or equal to the range of high sensitivity. For example, taking a quarter-wave plate as an example, its orientation angle and polarization angle are preferably within the range of ±5°.

[0037] Furthermore, in this embodiment, the polarization beam splitter and the image acquisition device are fixed on the same rotating displacement stage. This ensures that the polarization beam splitter can simultaneously acquire high-quality intensity information of both P-beams and S-beams during dynamic rotation. Furthermore, the light source used in this embodiment can be any parallel light source whose wavelength substantially matches the wavelength used on the waveplate.

[0038] Example 2

[0039] Corresponding to the above method embodiments, this embodiment discloses a detection system based on polarization information, including:

[0040] An object to be detected is placed between a laser source and a rotatable polarization beam splitter; the polarization beam splitter is used to simultaneously convert the polarized beam emitted from the object to be detected into P-beams and S-beams, the intensity distribution ratio of which changes dynamically with the rotation process.

[0041] An image acquisition device deployed after the polarization beam splitter is used to acquire and calculate the intensity distribution ratio of P-light and S-light as they dynamically change during rotation.

[0042] The control host, which is connected to the image acquisition device and the motor that drives the polarization beam splitter to rotate, is used to determine the first orientation angle corresponding to the polarization beam splitter when the light intensity distribution ratio is 1; then, based on the relative relationship between the polarization direction angle of the emitted beam corresponding to the object being detected when the light intensity distribution ratio is 1 and the orientation angle of the polarization beam splitter, the corresponding orientation angle parameter of the object being detected is located.

[0043] Preferably, the polarization beam splitter and the image acquisition device are fixed on the same rotary displacement stage.

[0044] Similarly, the object to be detected in this embodiment can be a first linear polarizer, whose polarization direction is determined by the orientation angle parameter detected and positioned; or the object to be detected can be a phase delayer placed between a second linear polarizer and the polarization beam splitter, whose fast axis direction is determined by the orientation angle parameter detected and positioned; wherein, the second linear polarizer is a standard component with a known polarization direction and is deployed between the laser source and the polarization beam splitter, and the second linear polarizer is stationary during the rotation of the polarization beam splitter.

[0045] In summary, based on the methods and systems disclosed in the above embodiments of the present invention, the present invention has at least the following beneficial effects:

[0046] 1. When the light intensity distribution ratio is 1, P-light and S-light are most sensitive to changes in polarization angle, which can maximize the detection accuracy.

[0047] 2. By using a single image acquisition device to simultaneously acquire the light intensity information of P-light and S-light, the errors caused by synchronous acquisition by multiple detectors and time-division acquisition by a single detector are avoided, thereby further improving the accuracy of the detection orientation angle parameter.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A detection method based on polarization information, characterized in that, include: The object to be tested is placed between a laser source and a rotatable polarization beam splitter; the polarization beam splitter is used to simultaneously convert the polarized beam emitted from the object to be tested into P-beams and S-beams, whose intensity distribution ratio changes dynamically with the rotation process. After the polarization beam splitter, an image acquisition device is used to acquire and calculate the intensity distribution ratio of P-light and S-light dynamically changing during the rotation process; When the light intensity distribution ratio is 1, determine the first orientation angle corresponding to the polarization beam splitter; then, based on the relative relationship between the polarization direction angle of the emitted beam corresponding to the object being detected and the orientation angle of the polarization beam splitter when the light intensity distribution ratio is 1, locate the corresponding orientation angle parameter of the object being detected. Wherein, the object to be detected is a first linear polarizer, and the orientation angle parameter located by detection is the polarization direction; or the object to be detected is a phase delayer placed between a second linear polarizer and the polarization beam splitter, and the orientation angle parameter located by detection of the phase delayer is the fast axis direction; wherein, the second linear polarizer is a standard component with a known polarization direction and is deployed between the laser source and the polarization beam splitter, and the second linear polarizer is stationary during the rotation of the polarization beam splitter.

2. The method according to claim 1, characterized in that, During the installation of the second linear polarizer and the phase retarder, it is estimated that the angle between the polarization direction of the second linear polarizer and the fast axis direction of the phase retarder is less than or equal to the estimated strong sensitivity range.

3. The method according to any one of claims 1 to 2, characterized in that, The polarization beam splitter and the image acquisition device are fixed on the same rotating displacement stage.

4. The method according to claim 3, characterized in that, The laser source is a monochromatic laser source.

5. A detection system based on polarization information, characterized in that, include: An object to be detected is placed between a laser source and a rotatable polarization beam splitter; the polarization beam splitter is used to simultaneously convert the polarized beam emitted from the object to be detected into P-beams and S-beams with a dynamic change in intensity distribution ratio during rotation. An image acquisition device deployed after the polarization beam splitter is used to acquire and calculate the intensity distribution ratio of P-light and S-light dynamically changing during the rotation process; The control host, which is connected to the image acquisition device and the motor that drives the polarization beam splitter to rotate, is used to determine the first orientation angle corresponding to the polarization beam splitter when the light intensity distribution ratio is 1; and then, based on the relative relationship between the polarization direction angle of the emitted beam corresponding to the object being detected when the light intensity distribution ratio is 1 and the orientation angle of the polarization beam splitter, the corresponding orientation angle parameter of the object being detected is located. Wherein, the object to be detected is a first linear polarizer, and the orientation angle parameter located by detection is the polarization direction; or the object to be detected is a phase delayer placed between a second linear polarizer and the polarization beam splitter, and the orientation angle parameter located by detection of the phase delayer is the fast axis direction; wherein, the second linear polarizer is a standard component with a known polarization direction and is deployed between the laser source and the polarization beam splitter, and the second linear polarizer is stationary during the rotation of the polarization beam splitter.

6. The system according to claim 5, characterized in that, The angle between the polarization direction of the second linear polarizer and the fast axis direction of the phase delayer is less than or equal to the estimated high sensitivity range.

7. The system according to any one of claims 5 to 6, characterized in that, The polarization beam splitter and the image acquisition device are fixed on the same rotating displacement stage.

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